The problem with suggesting things, is you never know what they are after.
Bottom line though I agree on basics. A GOOD trigger NEVER hurts.
Irons take desire to shoot well. Very FEW folks have desire to do anything that takes effort, they want the Mc Donalds route out... that means scopes.
The short guns seemingly take folks a bit more to master, even though IMHO there is no real mechanical difference. But I"m against collapsible stocks for beginners.
Of course that takes me back to what the normal AR was... 20 inches, but put optics on a flat top instead of irons... is best to start with.
While at it, get a trigger and float it, what the heck.. and again FMJ is not ammo. Well it isn't but it isn't much...
I have not looked at RRA books lately, when you have as many ARs and lowers as we have you tend not to keep up with goings on.... but I suspect that they would have something factory to fit the bill, trigger being the one thing that still could use some work or replacing, even the NM versions of the triggers.
There is no need to go the Wilson La Rue type route right away.
Don't you have a buffering article done somewhere? That can be important for folks. Though IMHO the 5.56 doesn't have recoil to start with, but smooth can make it even more fun.
